如何使用Flask-SQLAlchemy使用csv填充具有外键的模型？

Question

我有如下2模型类：

class Domain(db.Model): 
    __tablename__ = 'domain' 
    id = db.Column(db.Integer, primary_key=True) 
    domain_name = db.Column(db.String(30), unique=True) 
    mailboxes = db.Column(db.Integer, default=0) 

    def __init__(self, **kwargs): 
     self.__dict__.update(kwargs) 

    def __repr__(self): 
     return '%s' % self.domain_name 


class EmailAccount(db.Model): 
    __tablename__ = 'email_account' 
    __table_args__ = (
     db.UniqueConstraint('username', 'domain_id', 
          name='_uq_username_domain'),{} 
    ) 
    id = db.Column(db.Integer, primary_key=True) 
    username = db.Column(db.String(30)) 
    domain_id = db.Column(db.Integer, db.ForeignKey('domain.id')) 
    domain = db.relationship('Domain', backref=db.backref('emailaccounts', 
          lazy='dynamic')) 
    def __init__(self,**kwargs): 
     self.__dict__.update(kwargs) 

    def __repr__(self): 
     return '%s@%s ' % (self.username, self.domain) 

我仅添加了在这里的例子所需要的相关属性。我希望通过读取数据的csv文件来使用脚本填充模型。域表的脚本可以很好地使用Flask-SQLAlchemy，但emailaccount表的脚本会抛出异常。该脚本如下：

#Populate domains from csv 
domain_file = "domain.csv" 
csv_file = csv.DictReader(open(domain_file, 'rb'), delimiter=',') 
for row in csv_file: 
    #data type conversion from (csv)string before inserting to table 
    for key, value in row.items(): 
      #some code omitted 
     print key, value  
    domain = Domain(**row) 
    db.session.add(domain) 
    db.session.commit() 

#Populate accounts from csv 
accounts_file = "accounts.csv" 
csv_file = csv.DictReader(open(accounts_file, 'rb'), delimiter=',') 

for row in csv_file: 
    mdomain_name = '' 
    #data type conversion from (csv)string before inserting to table 
    for key, value in row.items(): 
     print key, value 
     if key == 'domain': 
      mdomain = Domain.query.filter_by(domain_name = value).first() 
      mdomain_name = mdomain.domain_name 
      mdomain_id = mdomain.id 
     if key == 'domain_id': 
      value = mdomain_id 
    account = EmailAccount(**row) 
    db.session.add(account) 
    db.session.commit() 

抛出异常是：

File "data.py", line 55, in db.session.add(account)
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 149, in do return getattr(self.registry(), name)(*args, **kwargs)
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1397, in add self._save_or_update_state(state)
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1415, in _save_or_update_state halt_on=self._contains_state):
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 1986, in cascade_iterator parent_dict, visited_states, halt_on))
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line 930, in cascade_iterator get_all_pending(state, dict_)
File ".../local/lib/python2.7/site-packages/sqlalchemy/orm/attributes.py", line 761, in get_all_pending ret = [(instance_state(current), current)] AttributeError: 'str' object has no attribute '_sa_instance_state'

PL。为data.py恢复脚本中代码的变化，即用于上传具有Domain类的外键的EmailAccount模型的数据的脚本。我只想使用Flask-SQLAlchemy。

提取accounts.csv文件：

Email Account,legacy_username,password,full_name,quota,is_domain_admin,is_catch_all,disabled_login,disabled_delivery 
info@abc.com,,,,104857600,,,, 
internal@abc.com,,,Internal,102400000,,,, 
kiran.rs@abc.com,,,,102400000,,,, kishorepr,xyz.com,,,,209715200,,,, 

Answer 1

当一行含有domain键，你取回域名，以获取其关键，但你没有你的row与域ID更新。

然后，当你这样做：

account = EmailAccount(**row) 

的row对象仍具有与域名相关的关键domain。由于您的EmailAccount类使用名称domain作为关系，所以db认为它将获得Domain对象，实际上，它将获得string（名称）。这就是为什么你得到错误AttributeError: 'str' object has no attribute '_sa_instance_state'。

更新：这应该工作

for row in csv_file: 
    account_values = {} 
    for key, value in row.items(): 
     if key == 'domain': 
      mdomain = Domain.query.filter_by(domain_name = value).first() 
      account_values['domain'] = mdomain 
     else: 
      account_values[key] = value 
    account = EmailAccount(account_values) 
    db.session.add(account) 
    db.session.commit()